HAVANA - Senior US and Cuban diplomats met Wednesday to discuss immigration issues amid tensions over the long detention of an American man on suspicion of spying.

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While the Cuban side described the talks as fruitful and respectful, US State Department spokesman P.J. Crowley was less effusive. He noted the US delegation again raised the issue of Alan Gross, a US government subcontractor held by Cuba without charge since December 3, 2009.

As for immigration, Crowley said in written comments sent from Washington that the two sides discussed areas of positive cooperation, as well as other issues "where there have been obstacles." He gave no details.

Deputy Cuban Foreign Minister Dagoberto Rodriguez, who led the Cuban delegation, said the two sides discussed ways to combat people-smuggling across the treacherous Straits of Florida.

"It was a fruitful exchange aimed at ... the establishment of more effective mechanisms of cooperation to combat illegal migrant smuggling," he said.

The Cuban government said both sides recognized that the number of Cubans attempting to get to the United States illegally, often in rickety rafts or inner tubes, had dropped significantly.

The American side was led by Roberta Jacobsen, the United States' principal deputy assistant secretary of state for Western Hemisphere affairs.

The gathering focused on a 17-year-old agreement under which the United States issues 20,000 visas to Cubans a year. But diplomats from both countries also use the twice-yearly meetings to detail a long-standing list of complaints, including Gross.

"As US officials have consistently done, the US delegation raised the case of Alan Gross ... and called for his immediate release," Crowley said.

US diplomats were also likely to have raised what Washington considers Cuba's spotty human-rights record overall.

The Cuban delegation, meanwhile, never fails to voice its opposition to the 48-year-old US trade embargo, which Havana says has put a stranglehold on the island's economy.

The Cuban statement said its officials also reiterated displeasure with a US policy that allows any Cuban reaching American soil to remain, while sending back those intercepted at sea. The Cubans have said in the past they believe the policy encourages people-smuggling.

Despite the many points of contention, the Cuban statement said the meeting "developed in an atmosphere of respect." It voiced Havana's willingness to hold another round of talks in six months.

US officials have made clear there is little hope for improved relations while Cuba holds Gross. They have also continued to call on Cuban authorities to open up the island's political system to democratic reform.

Relations have been sour for more than a half century, since shortly after Fidel Castro's revolution turned the island into a Soviet ally.

Hopes that President Barack Obama would usher in a new era in the relationship are long gone, replaced by the usual recriminations from both sides.

According to US diplomatic cables released by WikiLeaks, Cuban President Raul Castro - Fidel's brother, who has been running Cuba since 2006 - approached Washington about opening backdoor talks with the White House, but was rebuffed.